hold shift+control +alt and press S. A window will open and you can chose the quality to save your image. At the top right chose jpg for the image format. At the bottom right you’ll find width and height in pixels (this is the resolution of your image) if this number is too high then uploading time will be longer . Change the number you see to something smaller and save your image (make sure you change the name so you don’t lose your high resolution image). Let me know if this helped